U.S. patent number 8,480,350 [Application Number 12/442,137] was granted by the patent office on 2013-07-09 for turbofan engine with variable bypass nozzle exit area and method of operation.
This patent grant is currently assigned to United Technologies Corporation. The grantee listed for this patent is Michael Winter. Invention is credited to Michael Winter.
United States Patent |
8,480,350 |
Winter |
July 9, 2013 |
**Please see images for:
( Certificate of Correction ) ** |
Turbofan engine with variable bypass nozzle exit area and method of
operation
Abstract
A turbofan engine includes core and fan nacelles that provide a
bypass flow path having a nozzle exit area. The bypass flow path
carries a bypass flow to be expelled from the nozzle exit area. A
turbofan is arranged within the fan nacelle and upstream from the
core nacelle for generating the bypass flow. A flow control device
includes a surface in the bypass flow path including an aperture.
The flow device is adapted to introduce a fluid into the bypass
flow path for altering a boundary layer of the bypass flow that
effectively changes the nozzle exit area. In one example, bleed air
is introduced through the aperture. In another example, pulses of
fluid from a Helmholz resonator flow through the aperture. By
decreasing the boundary layer, the nozzle exit area is effectively
increased. By increasing the boundary layer, the nozzle exit area
is effectively decreased.
Inventors: |
Winter; Michael (New Haven,
CT) |
Applicant: |
Name |
City |
State |
Country |
Type |
Winter; Michael |
New Haven |
CT |
US |
|
|
Assignee: |
United Technologies Corporation
(Hartford, CT)
|
Family
ID: |
38124028 |
Appl.
No.: |
12/442,137 |
Filed: |
October 12, 2006 |
PCT
Filed: |
October 12, 2006 |
PCT No.: |
PCT/US2006/039993 |
371(c)(1),(2),(4) Date: |
March 20, 2009 |
PCT
Pub. No.: |
WO2008/045074 |
PCT
Pub. Date: |
April 17, 2008 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20100068039 A1 |
Mar 18, 2010 |
|
Current U.S.
Class: |
415/1 |
Current CPC
Class: |
F02K
1/30 (20130101); F02K 3/06 (20130101); F02K
1/16 (20130101); F02C 7/36 (20130101); F02C
6/08 (20130101); F05D 2260/4031 (20130101) |
Current International
Class: |
F01B
25/06 (20060101) |
Field of
Search: |
;415/1,144,331,117,143,914 ;60/204,206,267,262,39.17,226.1,226.2
;239/265.17 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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10 2004 024016 |
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Dec 2005 |
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923 996 |
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2 088 303 |
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Jan 1972 |
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FR |
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704 669 |
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Feb 1954 |
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GB |
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795 651 |
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May 1958 |
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GB |
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795 652 |
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May 1958 |
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GB |
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1 190 364 |
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May 1970 |
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GB |
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1 352 206 |
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May 1974 |
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GB |
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2 014 663 |
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Aug 1979 |
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GB |
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2 110 762 |
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Jun 1983 |
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GB |
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2 379 483 |
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Mar 2003 |
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GB |
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2 407 142 |
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Apr 2005 |
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GB |
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2008/045051 |
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Apr 2008 |
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WO |
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Other References
European Search Report for EP Application No. 11186123.3, Apr. 11,
2012. cited by applicant .
International Search Report for PCT Application No.
PCT/US2006/039993, Jul. 11, 2007. cited by applicant.
|
Primary Examiner: Gilman; Alexander
Attorney, Agent or Firm: Carlson, Gaskey & Olds,
P.C.
Claims
The invention claimed is:
1. A turbofan engine comprising: core and fan nacelles providing a
bypass flow path having a nozzle exit area, the bypass flow path
for carrying a bypass flow to be expelled from the nozzle exit
area; a turbofan arranged within the fan nacelle and upstream from
the core nacelle for generating the bypass flow; a spool having a
turbine mounted thereon and housed within the core nacelle; a gear
train interconnecting the turbofan and the spool, the turbofan
coupled to the spool through the gear train; a flow control device
including a surface in the bypass flow path including an aperture,
the flow device adapted to introduce a fluid into the bypass flow
path through the aperture for altering a boundary layer of the
bypass flow that effectively changes the nozzle exit area; and a
controller in communication with the flow control device, the
controller configured to determine when chan es in the effective
nozzle exit area are desired and command the flow control device to
obtain a desired boundary layer.
2. The turbofan engine according to claim 1, comprising a flow
source for providing the fluid.
3. The turbofan engine according to claim 2, comprising a
compressor arranged within the core nacelle, the compressor
providing bleed air as the fluid.
4. The turbofan engine according to claim 3, comprising a low spool
and a high spool rotatable relative to one another and housed
within the core nacelle, the compressor mounted on the high spool,
and the turbofan coupled to the low spool through the gear
train.
5. The turbofan engine according to claim 1, wherein the flow
control device includes a controller programmed to command a valve
for regulating a flow of the fluid through the aperture, wherein
the valve is closed during a cruise condition.
6. The turbofan engine according to claim 1, wherein the aperture
is arranged to introduce the fluid generally perpendicularly to the
bypass flow for increasing the boundary layer.
7. The turbofan engine according to claim 1, wherein the bypass
flow path extends axially along a radial space arranged between the
core and fan nacelles.
8. A turbofan engine comprising: core and fan nacelles providing a
bypass flow path having a nozzle exit area, the bypass flow path
for carrying a bypass flow to be expelled from the nozzle exit
area; a turbofan arranged within the fan nacelle and upstream from
the core nacelle for generating the bypass flow; a flow control
device including a surface in the bypass flow path including an
aperture, the flow device adapted to introduce a fluid into the
bypass flow path through the aperture for altering a boundary layer
of the bypass flow that effectively changes the nozzle exit area,
wherein the aperture is arranged to introduce the fluid generally
in the same direction as the bypass flow for decreasing the
boundary layer; a controller in communication with the flow control
device, the controller configured to determine when changes in the
effective nozzle exit area are desired and command the flow control
device to obtain a desired boundary layer; and a compressor
arranged within the core nacelle, the compressor providing bleed
air as the fluid.
9. The turbofan engine according to claim 8, wherein the bypass
flow path extends axially along a radial space arranged between the
core and fan nacelles.
10. A method of controlling a turbofan engine comprising the steps
of: determining when changes in the effective nozzle exit area of a
turbofan bypass flow path are desired; commanding a flow control
device to obtain a desired boundary layer by introducing a
compressor bleed air into a turbofan bypass flow path to alter a
bypass flow through the bypass flow path; and effectively changing
a nozzle exit area of the bypass flow path with the altered bypass
flow, including decreasing a boundary layer along a surface within
the bypass flow path thereby obtaining the desired boundary
layer.
11. The method according to claim 10, wherein the step of
effectively changing the nozzle exit area includes increasing a
boundary layer along a surface within the bypass flow path.
12. The method according to claim 10, wherein the bypass flow path
extends axially along a radial space arranged between a core
nacelle and a fan nacelle.
Description
This application claims priority to PCT Application Serial No.
PCT/US2006/039993, filed on Oct. 12, 2006.
BACKGROUND OF THE INVENTION
This invention relates to a turbofan engine, and more particularly,
the invention relates to effectively changing a nozzle exit area of
a bypass flow path.
A typical turbofan engine includes a spool supporting a compressor
and a turbine. The spool, compressor and turbine are housed within
a core nacelle. A turbofan, or "fan," is coupled to the spool and
is arranged upstream from the core nacelle. A fan nacelle surrounds
the turbofan and core nacelle. The fan and core nacelles provide a
bypass flow path having a nozzle exit area through which bypass
flow from the fan exits the engine.
Turbofan engines typical have a fixed nozzle exit area. The flow
through the nozzle affects, for example, the operational line of
the fan and compressor and the overall performance and efficiency
of the engine. Since the nozzle exit area is fixed, the operational
lines and other engine operating characteristics must be managed
using a more limited number of engine parameters. The engine
parameters are varied during engine operation to obtain desired
engine operating characteristics, such as fuel efficiency. What is
needed is a method and apparatus of managing engine operating
characteristics by using the nozzle exit area as an additional
variable parameter. What is also needs is an ability to use the
nozzle exit area as a variable parameter with minimal cost and
weight penalties.
SUMMARY OF THE INVENTION
A turbofan engine includes core and fan nacelles that provide a
bypass flow path having a nozzle exit area. In one example, the
nozzle exit area is fixed providing a physically constant size. The
bypass flow path carries a bypass flow circumventing the core
nacelle and expelled from the nozzle exit area. A turbofan is
arranged within the fan nacelle and upstream from the core nacelle
for generating the bypass flow. A flow control device includes a
surface in the bypass flow path including an aperture. The flow
device is adapted to introduce a fluid into the bypass flow path
for altering a boundary layer of the bypass flow that effectively
changes the nozzle exit area. In one example, bleed air is
introduced through the aperture. In another example, pulses of
fluid from a Helmholz resonator flow through the aperture. By
decreasing the boundary layer, the nozzle exit area is effectively
increased. By increasing the boundary layer, the nozzle exit area
is effectively decreased.
These and other features of the present invention can be best
understood from the following specification and drawings, the
following of which is a brief description.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view of an example turbofan engine.
FIG. 2a is a schematic partial side cross-sectional view of a
turbofan engine with an example flow control device expelling fluid
in a first manner.
FIG. 2b is a schematic partial end view of the turbofan engine
shown in FIG. 2a.
FIG. 3a is a schematic partial side cross-sectional view of a
turbofan engine with the example flow control device expelling
fluid in a second manner.
FIG. 3b is a schematic partial end view of the turbofan engine
shown in FIG. 3a.
FIG. 4 is a schematic partial side cross-sectional view of the
turbofan engine with another example flow control device.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
A geared turbofan engine 10 is shown in FIG. 1. A pylon 38 secures
the engine 10 to an aircraft. The engine 10 includes a core nacelle
12 that houses a low spool 14 and high spool 24 rotatable about an
axis A. The low spool 14 supports a low pressure compressor 16 and
low pressure turbine 18. In the example, the low spool 14 drives a
turbofan 20 through a gear train 22. The high spool 24 supports a
high pressure compressor 26 and high pressure turbine 28. A
combustor 30 is arranged between the high pressure compressor 26
and high pressure turbine 28. Compressed air from compressors 16,
26 mixes with fuel from the combustor 30 and is expanded in
turbines 18, 28.
In the examples shown, the engine 10:1 is a high bypass turbofan
arrangement. In one example, the bypass ratio is greater than 10,
and the turbofan diameter is substantially larger than the diameter
of the low pressure compressor 16. The low pressure turbine 18 has
a pressure ratio that is greater than 5:1, in one example. The gear
train 22 is an epicycle gear train, for example, a star gear train,
providing a gear reduction ratio of greater than 2.5:1. It should
be understood, however, that the above parameters are only
exemplary of a contemplated geared turbofan engine. That is, the
invention is applicable to other engines including direct drive
turbofans.
Airflow enters a fan nacelle 34, which surrounds the core nacelle
12 and turbofan 20. The turbofan 20 directs air into the core
nacelle 12, which is used to drive the turbines 18, 28, as is known
in the art. Turbine exhaust E exits the core nacelle 12 once it has
been expanded in the turbines 18, 28, in a passage provided between
the core nacelle and a tail cone 32.
The core nacelle 12 is supported within the fan nacelle 34 by
structure 36, which are commonly referred to as upper and lower
bifurcations. A generally annular bypass flow path 39 is arranged
between the core and fan nacelles 12, 34. The example illustrated
in FIG. 1 depicts a high bypass flow arrangement in which
approximately eighty percent of the airflow entering the fan
nacelle 34 bypasses the core nacelle 12. The bypass flow B within
the bypass flow path 39 exits the fan nacelle 34 through a nozzle
exit area 40.
For the engine 10 shown in FIG. 1, a significant amount of thrust
may be provided by the bypass flow B due to the high bypass ratio.
Thrust is a function of density, velocity and area. One or more of
these parameters can be manipulated to vary the amount and
direction of thrust provided by the bypass flow B. In one example,
the engine 10 includes a structure associated with the nozzle exit
area 40 to change the physical area and geometry to manipulate the
thrust provided by the bypass flow B. However, it should be
understood that the nozzle exit area may be effectively altered by
other than structural changes, for example, by altering the
boundary layer, which changes the flow velocity. Furthermore, it
should be understood that any device used to effectively change the
nozzle exit area is not limited to physical locations near the exit
of the fan nacelle 34, but rather, includes altering the bypass
flow B at any suitable location.
The engine 10 has a flow control device 41 that is used to
effectively change the nozzle exit area. In one example, the flow
control device 41 provides the fan nozzle exit area 40 for
discharging axially the bypass flow B pressurized by the upstream
turbofan 20 of the engine 10. A significant amount of thrust is
provided by the bypass flow B due to the high bypass ratio. The
turbofan 20 of the engine 10 is designed for a particular flight
condition, typically cruise at 0.8 M and 35,000 feet. The turbofan
20 is designed at a particular fixed stagger angle for an efficient
cruise condition. The flow control device 41 is operated to vary
the nozzle exit area 40 to adjust fan bypass air flow such that the
angle of attack or incidence on the fan blade is maintained close
to design incidence at other flight conditions, such as landing and
takeoff. This enables desired engine operation over a range of
flight condition with respect to performance and other operational
parameters such as noise levels. In one example, the flow control
device 41 defines a nominal converged position for the nozzle exit
area 40 at cruise and climb conditions, and radially opens relative
thereto to define a diverged position for other flight conditions.
The flow control device 41 provides an approximately 20% change in
the exit nozzle area 40.
Referring to FIGS. 2a-4, a flow control device is shown that uses a
fluid, such as air, to vary a boundary layer Q within the bypass
flow path 39 to effectively change the nozzle exit area 40. The
boundary layer Q is created by the bypass flow B along the walls of
the bypass flow path 39.
In the examples shown in FIGS. 2a-3b, the flow control device 41
uses bleed air L from one of the compressor stages 54. The bleed
air L is introduced to the bypass flow path 39 in a desired manner
to affect the boundary layer Q. It is typically desirable to
extract bleed air L from the lowest usable compressor stage to
minimize the efficiency impact on the engine. In one example, the
compressor stage 54 corresponds to an upstream compressor stage on
the high compressor 26. In one example, extraction of bleed air L
is avoided during particular engine operating conditions, such as
cruise.
In one example, a controller 50 commands a valve 55 arranged in a
passage 52. The passage 52 fluidly connects the compressor stage 54
to apertures 56 arranged on a surface 57 adjacent to the bypass
flow path 39. Three apertures 56 are shown for exemplary purposes.
The apertures 56 can be arranged in an array and plumbed in any
suitable manner. The valve 55 selectively regulates the bleed air L
provided through the apertures 56 in response to commands from the
controller 50 to obtain a desired boundary layer thickness. The
controller 50 determines when changes in the effective nozzle exit
area 40 are desired for a particular engine operating
characteristic.
Decreasing the boundary layer at the surface 57 effectively "opens"
the nozzle exit area 40. A decrease in boundary layer Q increases
the mean velocity of bypass flow B across the nozzle exit area 40.
Conversely, decreasing the boundary layer Q at the surface 57
effectively "closes" the nozzle exit area 40. An increase in
boundary layer decreases the mean velocity of bypass flow B across
the nozzle exit area 40.
In the example shown in FIGS. 2a-2b, the apertures 56 introduce the
bleed air L in a direction generally perpendicular to the bypass
flow B, which effectively increases the boundary layer Q and
provides and effective closing of the nozzle exit area 40. The
bypass flow B in FIGS. 2b and 3b are indicated in a generally axial
direction.
In the example shown in FIGS. 3a-3b, the apertures 56' are arranged
generally tangentially to the bypass flow B so that introducing the
bleed air L effectively opens the nozzle exit area 40 by decreasing
the boundary layer.
In either approach shown in FIGS. 2a-2b and FIGS. 3a-3b, the bleed
air L provides a range of effective nozzle exit areas 40 between
no-bleed flow and bleed flow conditions. Said another way, in one
example, one of the aperture orientations shown in the Figures is
chosen. With the chosen aperture configuration, the flow of bleed
air L is adjusted to obtain the desired boundary layer Q. In this
manner, the flow control device 41 provides another engine
parameter by which the engine operating characteristics can be
managed.
Another example flow control device 41' is shown in FIG. 4. In one
example, the flow control device 41' uses a chamber 58 to provide
pulsed flow to the surface 57 through passages 60 to the apertures
56. In one example, the chamber 58 is tuned to provide air to the
bypass flow path 39 at a desired frequency. An exciter 64 is
actuated by a driver 66 in response to a command from the
controller 50. The exciter 64 create pulses that are delivered to
through the apertures 56 to change the boundary layer Q. The driver
66 modulates the exciter 64 at a desired frequency to obtain a
desired boundary layer Q. The aperture 56 and chamber 58 geometry
are selected to achieve the desired boundary layer Q. The apertures
56 can be arranged in any suitable manner, for example in the
manner described above relative to FIGS. 2a-3b.
Although an example embodiment of this invention has been
disclosed, a worker of ordinary skill in this art would recognize
that certain modifications would come within the scope of this
invention. For that reason, the following claims should be studied
to determine the true scope and content of this invention.
* * * * *